Device and method for interconnecting a tanker and a floating terminal

ABSTRACT

A device for connecting a floating vessel such as a tanker ( 3 ) and a floating, fixedly orientated, terminal ( 1 ), where a floating coupling unit ( 2 ) which is provided with a contact portion ( 211 ) arranged to be able to bear against a portion of the tanker ( 3 ), is shiftably allocated said terminal ( 1 ), in that at least two mooring means ( 24 ) extend from said terminal ( 1 ) via respective shifting devices ( 23 ) arranged on the coupling unit ( 2 ), and to respective anchors ( 25 ) arranged at a distance from said terminal ( 1 ) is described. A method for connecting a floating vessel ( 3 ) and a terminal ( 1 ) for fluids by means of a floating coupling unit ( 2 ) is also described.

The invention relates to a device for interconnecting a tanker, and afloating loading or offloading terminal for fluids, where the terminalis fixedly orientated, and where a floating coupling unit is shiftablyassociated with said terminal. Further, the invention concerns a methodof connecting a tanker and a by means of a floating coupling unit.

Transfer of cargo between a tanker and a floating unit (e.g. a loadingor offloading terminal, or production platform) requires comprehensivemeasures regarding mooring and/or anchoring. The applicant's own patentapplication NO 20064700 (corresponding to WO 2008082306) describes amooring system for a conventional tanker, i.e. a tanker without adynamic positioning system and bow loading equipment, where the tankeris connected to the floating loading/offloading terminal which isfixedly orientated. The tanker is moored in four points, where two ofthe moorings are connected to the terminal and two moorings are fastenedto buoys anchored remote from the terminal. The tanker is thentransferred in relation to the terminal by tightening, respectivelyslackening, of the respective moorings until the tanker has reached thedesired position for loading or offloading.

It is necessary to keep a certain distance between the terminal and thetanker during the loading or offloading operation, especially when theoperation takes place during rough weather conditions with strong winds,waves and currents. It is therefore difficult to transfer hoses andsimilar for the transfer of cargo etc. between the terminal and thetanker.

The object of the invention is to remedy or to reduce at least one ofthe disadvantages of the prior art, or at least to provide a usefulalternative to the prior art.

The object is achieved by features stated in the below description andin the following patent claims.

The applicant's own patent application NO 20064700 (corresponding to WO2008082306) is in its entirety incorporated as a reference in thisdescription.

In the following, the term “loading terminal” is used for the sake ofconvenience, although the invention in principle also can be appliedduring offloading, i.e. when transferring cargo from a tanker and to theterminal for storing or processing there. The invention is alsoapplicable for connecting a ship, such as a tanker, to a productionplatform, a floating facility for handling liquefied natural gas (FLNG),etc.

To a floating loading terminal which is fixedly oriented by means ofsuitable anchor and/or propulsion means, typically propulsion machinerywith an associated installation for dynamic positioning, there is anassociated a floating coupling unit which can be shifted between aninactive position close to the loading terminal and an active positionbearing against a portion of the tanker by means of a mooring system.The coupling unit is provided with a ballasting system arranged to varythe net buoyancy of the coupling unit. The coupling unit is providedwith an immersed, horizontal portion which at least partly is arrangedto extend underneath a bottom portion of the tanker, for example by thecoupling unit being generally L-shaped. Said horizontal portion isprovided with a generally upward facing contact portion arranged to beable to bear against said bottom portion of the tanker by deballastingthe coupling unit after it is placed in the desired position forcoupling with the tanker. The coupling unit is provided with mooringmeans connecting it to at least two mooring points on the loadingterminal and to at least two anchoring points remote from the loadingterminal via associated winches. The coupling unit may thus be pulled ina desired direction towards or away from the tanker. The mooring meanscan extend continuously between the loading terminal and to theanchoring points via coupling points on the coupling unit, where themooring means run over shifting means arranged to pull the coupling unitalong the mooring means. In this embodiment it is an advantage if themooring means are connected to the loading terminal via constant tensionmeans, typically via constant tension winches, to maintain a constanttension in the mooring means independent of tide and wave inducedmovement in the loading terminal and the coupling unit, and independentof the distance from the coupling unit to the loading terminal.Alternatively, the mooring means may be divided in two, as they extendfrom mooring winches arranged on the coupling unit. In this embodimentit is also an advantage if the mooring system comprises means formaintaining constant tension in the mooring means, for example by themooring winches being constant tension winches or that the mooring meansconnecting the coupling unit to the loading terminal, are connected toconstant tension means arranged on the loading terminal.

The coupling unit is preferably provided with a vertical portion risingabove the body of water and being provided with one or more manipulatorsarranged to transfer one or more transport lines for connection with ordisconnection from a loading/offloading manifold which on a tankerpreferably is arranged amidships. At least a portion of the transportlines extending between the loading terminal and the coupling unit isformed of a flexible material such that a fluid communicating connectionis maintained between the loading terminal and the coupling unitindependent of the position of the coupling unit relative to the loadingterminal. The coupling unit may be provided with suitable lifting meansfor connection with the transport line(s) and possibly other linesextending between the loading terminal and the coupling unit to relievesaid lines, typically in the form of one or more protruding crane arms.

The terminal may typically be a floating production, storage andoffloading facility (FPSO), more typical a floating facility forhandling liquefied natural gas (FLNG).

In a first aspect the invention relates to more specifically a devicefor interconnecting a tanker and a floating terminal, where saidterminal is fixedly orientated, characterized in that a floatingcoupling unit provided with at least one contact portion is configuredfor bearing against at least a portion of the tanker, is shiftablyassociated with said terminal, in that at least two mooring means areconfigured for extending between the terminal via respective shiftingdevices arranged on the coupling unit, and respective anchors arrangedat a distance from said terminal.

The coupling unit may be provided with a vertical portion rising above awater surface and being provided with means for suspending and/orrelocating of one or more line portions extending between said terminaland the coupling unit and is arranged for disconnectable connection withthe tanker.

The coupling unit may be provided with a ballasting system.

Said mooring means may comprise a first portion extending between saidterminal and the coupling unit, and a second portion extending betweenthe coupling unit and the respective anchor, as each of the mooringmeans portions are connected to a shifting device arranged on thecoupling unit.

The shifting unit may be a constant tension winch.

Said first mooring means may be connected to said terminal viarespective tensioning devices.

Said terminal may be a floating production, storing and offloadingfacility (FPSO) or a floating facility for handling liquefied naturalgas (FLNG).

In a second aspect, the invention more specifically relates to a methodof connecting a tanker and a fixedly oriented terminal, where saidterminal is fixedly orientated, and where the method comprises the stepsof:

-   -   mooring the tanker with at least two ship moorings to said        terminal and with at least two ship moorings to respective        anchors;    -   shifting the tanker by tightening, possibly slacken, the        respective ship moorings until the tanker has arrived at a        desired position relative said terminal;        characterized in that the method further comprises the steps of:    -   shifting a floating coupling unit by means of shifting devices        engaged with at least two mooring means extending from said        terminal via respective shifting devices arranged on the        coupling unit, and to respective anchors arranged at a distance        from said terminal, to supportive contact against a portion of        the tanker;    -   deballasting the coupling unit at least until a submerged,        generally horizontal contact portion of the coupling unit is        supportively bearing against a portion of the tanker bottom;    -   connecting the tanker and said terminal in a fluid communicating        way by maneuvering an end portion of at least one fluid        transport line to connect with a loading/offloading manifold        arranged on the tanker.

The method may further comprise the step of:

-   -   maintaining a prescribed pre-tensioning in the mooring means by        activating one or more constant tension winches in a locking        engagement with the respective mooring means.

In the following, an example of a preferred embodiment is describedwhich is illustrated in the attached drawings, where:

FIG. 1 shows a plan view of a loading terminal provided with a couplingunit according to the invention anchored in a body of water;

FIG. 2 shows in plan view a situation where a tanker is anchored by theloading terminal and the coupling unit bears against the tanker;

FIG. 3 shows in a section view and on a larger scale a side view of thecoupling unit connected to the tanker.

In the figures the reference number 1 indicates a loading terminal,typically in the form of a floating facility for handling liquefiednatural gas (FLNG), anchored in a body of water 4 by means of severalanchoring means 13 extending between said terminal 1 and respectivefirst anchors 131 arranged on a seabed 42 at a distance from theterminal 1.

A floating coupling unit 2 is associated with the terminal 1 as thecoupling unit 2 is shiftable relative to the terminal 1 in that thecoupling unit 2 is connected with mooring means 24 extending from theterminal 1 via respective shifting devices 23 arranged on the couplingunit 2 and to other anchors 25 arranged at a distance from each other onthe seabed 42. The coupling unit 2 is provided with an approximatelyhorizontal, upward facing contact portion 211 arranged to be able toextend underneath a portion of a bottom 31 of a tanker 3. The contactportion 211 is preferably provided with several elastic contact cushions21 la arranged to protect the contact portion 211 and the bottom 31 ofthe ship. The coupling unit 2 is provided with a ballasting system 26utilized for raising and lowering the coupling unit 2 in relation to thetanker 3 to contact, respectively clearance, between the contact portion211 and the bottom 31 of the ship.

A vertical portion 22 of the coupling unit 2 rises above the body ofwater 4. In the shown embodiment the coupling unit 2 is suitablyL-shaped. The vertical portion 22 is provided with fenders 221 arrangedfor supportive contact against a side 32 of the ship. On the rising,vertical portion 22 of the coupling unit 2 manipulators 27 and liftingdevices 28 are arranged, connected to fluid transport and control lines11, 12 extending from the terminal 1 to the coupling unit 2 and beingprovided with end portions arranged for connection to a suitable loadingmanifold 33 on the tanker 3. The manipulators 27 of a type which per seis known, are arranged to maneuver the end portions of said lines 11, 12during connection and disconnection, and the lifting devices 28 arearranged to hold the portion of the lines 11, 12 extending between theterminal 1 and the coupling unit 2, and prevent these from beingoverloaded during shifting of the coupling unit 2. The signal line 12transmits relevant control signals between the terminal 1 and thecoupling unit 2 and between the coupling unit 2 and the tanker 3. Thecontrol line 12 may also transmit energy for operation of electricalsystems on the coupling unit 2.

The shifting devices 23 of the coupling unit 2 are in a first embodimentwinches connected to a first mooring mean portion 241 extending betweenthe coupling unit 2 and the terminal 1, respectively a second mooringmean portion 242 extending between the coupling unit 2 and therespective second anchor 25. The winches 23 are preferably constanttension winches.

In a second embodiment the mooring means 24 run uninterrupted betweenthe terminal 1 via the coupling unit 2, where the shifting device 23 isengaged with the mooring means 24, and to the respective second anchor25. That portion of the mooring means 24 which is engaged with theshifting device 23 may typically be a chain portion running over one orseveral sprocket wheels (not shown). In this embodiment the mooringmeans 24 is preferably connected to the terminal 1 via a tensioningdevice 14, for example a constant tension winch.

The purpose of employing constant tension winches as a shifting device25 or a tensioning device 14 is to prevent slacking or overtensioning ofthe coupling unit 2 mooring means 24 when the coupling unit 2 is shiftedor is moved vertically due to ballasting, etc.

The tanker 3 is moored by means of ship moorings 34, 34′ to the anchors25, and the terminal 1, respectively, for example as disclosed in NO20064700.

When the tanker 3 is arranged in the desired position for transferringcargo, the ballasted coupling unit 2 is shifted by means of the shiftingdevices 23 and the mooring means 24 to alongside contact against theside 32 of the ship as the horizontal portion 21 is extended underneatha portion of the bottom 31 of the ship and the lifting devices 28 areoperated such that the lines 11, 12 follow the movement of the couplingunit 2 relative to the terminal 1. The coupling unit 2 is thendeballasted such that the contact cushions 211 a on the horizontal,upward facing contact portion 211 are bearing supportively against thebottom 31 of the ship. The lines 11, 12 are connected to the tanker 3,and transfer of fluid between the terminal 1 and the tanker 3 can becarried out.

When the transfer of fluid between the terminal 1 and the tanker 3 hasbeen carried out, the lines 11, 12 are disconnected from theloading/offloading manifold 33 of the tanker 3, the coupling unit 2 isballasted such that it is released from the bottom 31 of the ship. Thecoupling unit 2 is then shifted away from the tanker 3 to a positionclose to the terminal 1.

1. A device for interconnecting a tanker and a floating terminal, wheresaid terminal is fixedly orientated, the device comprising: a floatingcoupling unit provided with at least one contact portion configured forbearing against at least a portion of the tanker; at least two mooringmembers configured for extending between the terminal, via respectiveshifting devices arranged on the coupling unit , and respective anchorsarranged at a distance from said terminal; wherein the coupling unit isshiftably arranged with respect to the terminal.
 2. The device of claim1, wherein the coupling unit is provided with a vertical portion risingabove a water surface and is provided with a member for suspendingand/or relocating of one or more line portions extending between theterminal and the coupling unit and are arranged to disconnectablyconnect with the tanker.
 3. The device of claim 1, wherein the couplingunit is provided with a ballasting system.
 4. The device of claim 1,wherein said mooring members comprise a first portion extending betweenthe terminal and the coupling unit, and a second portion extendingbetween the coupling unit and the respective anchor, as each of themooring portions are connected to a shifting device arranged on thecoupling unit.
 5. The device of claim 4, wherein the shifting device isa constant tension winch.
 6. The device of claim 1, wherein said firstmooring members are connected to the terminal via respective tensioningdevices.
 7. The device of claim 1, wherein the terminal is a floatingproduction, storage and offloading facility or a floating facility forhandling liquefied natural gas.
 8. The device of claim 1, wherein theterminal is fixedly oriented by means of suitable an anchoring memberand/or propulsion machinery connected to facilities for dynamicpositioning.
 9. A method of interconnecting a tanker and a fixedlyorientated terminal , comprising the steps of: mooring the tanker withat least two ship moorings to the terminal and with at least two ship torespective anchors , shifting the tanker by tightening, possiblyslacken, the respective ship moorings (34, 34′) until the tanker hasarrived at a desired position relative to the terminal, shifting afloating coupling unit by means of shifting devices in engagement withat least two mooring members extending from the terminal via respectiveshifting devices arranged on the coupling unit , and to respectiveanchors arranged at a distance from the terminal , to supporting contactagainst a portion of the tanker.
 10. The method of claim 9, furthercomprising the steps of: deballasting the coupling unit at least until asubmerged, generally horizontal contact portion of the coupling unit issupportingly bearing against a portion of the bottom of the tanker; andconnecting the tanker and said terminal in a fluid communicating way bymaneuvering an end portion of at least one fluid transport line toconnecting with a loading/offloading manifold arranged on the tanker.11. The method of claim 8, further comprising the step of maintaining aprescribed pre-tensioning in the mooring members by activating one ormore constant tension winches in a locking engagement with therespective mooring members.